Does a Filter Produce Enough Air for Fish?

Both fish and invertebrates "breathe" oxygen through their gills and skin and need oxygenated water to thrive. Water movement and turbulence helps oxygen dissolve in the water. Most aquarium filters provide adequate water movement for this purpose. However, in some situations, you might need supplemental water pumps for proper water oxygenation.

  1. Oxygenation

    • Gas exchange -- picking up oxygen and shedding carbon dioxide -- happens at the surface of water. Water movement and turbulence improve this. Almost all aquarium filters move water around in some way, generating sufficient water movement for many fish. However, some species high metabolic demands that require extra water movement and oxygen. In these cases, your tank might need extra pumps or filters to move extra water. Using an aquarium oxygen test kit, look for a level of at least 7ppm. Without a test kit, watch for signs of low oxygen in your fish including lethargy, gasping at the water surface and flapping their gill covers more rapidly than usual.

    When a Filter Isn't Enough

    • Some fish need extra oxygen. For example, very active ones such as tangs need extra oxygen because they swim constantly. Additionally, some river-dwelling fish such as hillstream loaches need extra water movement since they have adapted to temperate fast-moving rivers. If fish don't have enough oxygen in their water, they become lethargic, flap their gills faster than normal and gasp at the water's surface. If you see these signs, or have species with high oxygen needs, supplement your filter with other oxygenation options.

    Oxygenation Options

    • If your fish need more oxygen, you have several options. Airstones consist of porous rock or wood connected to an air pump. These generate bubbles, which create some water movement and turbulence at the water's surface. While this option costs the least, it is also the least effective. You can also use powerhead water pumps to generate water movement. Adding more filters generates extra water movement as a byproduct of filtration. All types of aquarium filters can enhance oxygenation, including everything from cheap sponge filters to elaborate trickle filters. In most cases, adding additional water pumps achieves the same effect while remaining cost-effective.

    Wavemakers

    • Some marine organisms have adapted to the movement of waves, not just simple water movement. Without these surging motions, some coral cannot survive in home aquariums. Aquarium wavemakers generate these currents by moving powerheads back and forth or by turning one or more powerheads on and off in sequence to generate wavelike underwater motion; they don't make waves on the surface of your tank. Additionally, this wave motion improves oxygenation more than a simple water pump, making it ideal for fish that require more oxygen, including both freshwater and marine species.